dict

Key-Value Dictionary

Dict implements a Key - Value dictionary.
The representation of a dictionary is not defined.

This module provides exactly the same interface as the module
orddict. One difference is that while this module
considers two keys as different if they do not match (=:=),
orddict considers two keys as different if and only if
they do not compare equal (==).

DATA TYPES

dictionary()
as returned by new/0

Functions

append(Key, Value, Dict1) -> Dict2

Key = Value = term()

Dict1 = Dict2 = dictionary()

This function appends a new Value to the current list
of values associated with Key. An exception is
generated if the initial value associated with Key is
not a list of values.

append_list(Key, ValList, Dict1) -> Dict2

ValList = [Value]

Key = Value = term()

Dict1 = Dict2 = dictionary()

This function appends a list of values ValList to
the current list of values associated with Key. An
exception is generated if the initial value associated with
Key is not a list of values.

erase(Key, Dict1) -> Dict2

Key = term()

Dict1 = Dict2 = dictionary()

This function erases all items with a given key from a
dictionary.

fetch(Key, Dict) -> Value

Key = Value = term()

Dict = dictionary()

This function returns the value associated with Key
in the dictionary Dict. fetch assumes that
the Key is present in the dictionary and an exception
is generated if Key is not in the dictionary.

fetch_keys(Dict) -> Keys

Dict = dictionary()

Keys = [term()]

This function returns a list of all keys in the dictionary.

filter(Pred, Dict1) -> Dict2

Pred = fun(Key, Value) -> bool()

Key = Value = term()

Dict1 = Dict2 = dictionary()

Dict2 is a dictionary of all keys and values in
Dict1 for which Pred(Key, Value) is true.

find(Key, Dict) -> {ok, Value} | error

Key = Value = term()

Dict = dictionary()

This function searches for a key in a dictionary. Returns
{ok, Value} where Value is the value associated
with Key, or error if the key is not present in
the dictionary.

fold(Fun, Acc0, Dict) -> Acc1

Fun = fun(Key, Value, AccIn) -> AccOut

Key = Value = term()

Acc0 = Acc1 = AccIn = AccOut = term()

Dict = dictionary()

Calls Fun on successive keys and values of
Dict together with an extra argument Acc
(short for accumulator). Fun must return a new
accumulator which is passed to the next call. Acc0 is
returned if the list is empty. The evaluation order is
undefined.

from_list(List) -> Dict

List = [{Key, Value}]

Dict = dictionary()

This function converts the key/value list List to a
dictionary.

is_key(Key, Dict) -> bool()

Key = term()

Dict = dictionary()

This function tests if Key is contained in
the dictionary Dict.

map(Fun, Dict1) -> Dict2

Fun = fun(Key, Value1) -> Value2

Key = Value1 = Value2 = term()

Dict1 = Dict2 = dictionary()

map calls Func on successive keys and values
of Dict to return a new value for each key.
The evaluation order is undefined.

merge(Fun, Dict1, Dict2) -> Dict3

Fun = fun(Key, Value1, Value2) -> Value

Key = Value1 = Value2 = Value3 = term()

Dict1 = Dict2 = Dict3 = dictionary()

merge merges two dictionaries, Dict1 and
Dict2, to create a new dictionary. All the Key
- Value pairs from both dictionaries are included in
the new dictionary. If a key occurs in both dictionaries then
Fun is called with the key and both values to return a
new value. merge could be defined as:

new() -> dictionary()

size(Dict) -> int()

store(Key, Value, Dict1) -> Dict2

This function stores a Key - Value pair in a
dictionary. If the Key already exists in Dict1,
the associated value is replaced by Value.

to_list(Dict) -> List

Dict = dictionary()

List = [{Key, Value}]

This function converts the dictionary to a list
representation.

update(Key, Fun, Dict1) -> Dict2

Key = term()

Fun = fun(Value1) -> Value2

Value1 = Value2 = term()

Dict1 = Dict2 = dictionary()

Update the a value in a dictionary by calling Fun on
the value to get a new value. An exception is generated if
Key is not present in the dictionary.

update(Key, Fun, Initial, Dict1) -> Dict2

Key = Initial = term()

Fun = fun(Value1) -> Value2

Value1 = Value2 = term()

Dict1 = Dict2 = dictionary()

Update the a value in a dictionary by calling Fun on
the value to get a new value. If Key is not present
in the dictionary then Initial will be stored as
the first value. For example append/3 could be defined
as: